There are many ways your phone can provide glimpses into your personality: Your choice of apps, your music and photos, even the brand of smartphone you buy, to name a few. But new research reveals another surprising piece to the what-your-cell-says-about-you puzzle. Turns out analyzing the molecules, chemicals, and microbes left behind on a mobile device can tell a lot about its owner—including the person's diet, health status, probable gender, and more.

The new study, published in the Proceedings of the National Academy of Sciences, suggests that this type of profiling could one day be useful for clinical trials, medical monitoring, airport screenings, and criminal investigations. It also serves as a reminder of the lasting chemical residues of the foods we eat, the cosmetics we wear, and the places we visit. In some cases, researchers could pinpoint ingredients from personal-care products that the owner of the phone hadn’t used in six months!

"You can imagine a scenario where a crime-scene investigator comes across a personal object—like a phone, pen, or key—without fingerprints or DNA, or with prints or DNA not found in the database," said senior author Pieter Dorrestein, PhD, professor of chemistry and biochemistry at the University of California San Diego School of Medicine, in a press release. "So we thought—what if we take advantage of left-behind skin chemistry to tell us what kind of lifestyle this person has?"

Dorrestein’s previous research has shown that molecules analyzed from skin swabs tend to contain traces of hygiene and beauty products, even when people haven’t applied them for a few days. "All of these chemical traces on our bodies can transfer to objects," Dorrestein said. "So we realized we could probably come up with a profile of a person's lifestyle based on chemistries we can detect on objects they frequently use."

For their new study, Dorrestein and his colleagues swabbed four spots on the cell phones of 39 volunteers, and used a technique called mass spectrometry to detect molecules from those samples. Then, they compared those molecules with ones indexed in a large, crowd-sourced reference database run by UCSD.

With this information, the researchers developed a personalized lifestyle "read-out" from each phone. They were able to determine certain medications that the volunteers took—including anti-inflammatory and anti-fungal skin creams, hair loss treatments, antidepressants, and eye drops. They could identify food that had recently been eaten, such as citrus, caffeine, herbs, and spices. And they detected chemicals, like those found in sunscreen and bug spray, months after they’d last been used by the phones’ owners.

"By analyzing the molecules they've left behind on their phones, we could tell if a person is likely female, uses high-end cosmetics, dyes her hair, drinks coffee, prefers beer over wine, likes spicy food, is being treated for depression, wears sunscreen and bug spray—and therefore likely spends a lot of time outdoors—all kinds of things," said first author Amina Bouslimani, PhD, an assistant project scientist in Dorrestein's lab. In fact, the researchers were able to correctly predict that one study participant was a camper or backpacker because of residue from DEET and sunscreen ingredients on her phone.

This was a proof-of-concept study, meaning that it only showed that the technology exists—not that it's ready for market. To develop even more precise profiles, and to be useful in the real world, the researchers say more molecules are needed in the reference database. They hope it will grow to include more common items including foods, clothing materials, carpets, and paints, for example.

Dorrestein and Bouslimani are conducting further studies with an additional 80 people and samples from other personal objects, such as wallets and keys. They hope that eventually, molecular profiles will be useful in medical and environmental settings.

Doctors might employ this technique to determine whether a patient really is taking his or her medication, for example. Or scientists could use it to determine people’s exposure to toxins in high-risk workplaces or neighborhoods near potential pollution sources. And, of course, molecular profiling could help criminal investigators by narrowing down the potential owners of objects, or understanding people’s habits based on items they touch, they wrote in their paper.

As creepy as all this may sound, personality-specific microbes likely aren't the most alarming things hiding on your cell phone. Other research shows that our tech devices are popular spots for germs like the flu virus and antibiotic-resistant Staphylococcus aureus (MRSA).

Unless you plan to rob a bank and leave your phone behind as evidence, germs are probably your biggest threat at the moment. To keep buildup to a minimum, and harmful bugs at bay, try to remember to clean your screen and case regularly with a disinfectant wipe.